New possibilities in isotope correlation analysis of spent nuclear fuel

Isotopic correlation analysis is believed to make possible quick and accurate determinations of nuclear fuel parameters for reactor operation, reprocessing, fuel management and nuclear safeguards. Correlation dependencies have been found between ratios of fission products on the one hand and isotope ratios of the heavy elements on the other hand. The use of the¹⁵⁴Eu/¹⁵⁵Eu ratio in correlation analysis was proposed by SMULEK. The scope of useful applications of this isotopic ratio has been further investigated. A quick and time-saving method to measure the¹⁵⁴Eu/¹⁵⁵Eu ratio has been elaborated. The atomic ratios have been found by internal calibration using the computer programme ABSINT. Beside this the atomic ratios of¹⁵⁴Eu/¹⁵⁵Eu as a function of nuclear fuel burn-up have been calculated using the computer programme ISOTOP. The correlation between the¹⁵⁴Eu/¹⁵⁵Eu ratio and nuclear fuel burn-up is best approximated by a quadratic function. Up to a burn-up of 1% fima a linear function can be used.     

On longitudinal impact IV

Summary A survey is given of common pile-driving formulae, and special attention is paid to the so-called dynamic formulae whose characteristic features are compiled in a table and a diagram. The well-known situation that these formulae are fairly reliable for drop-hammers (heavy rams) but quite unreliable for double-acting compressed air hammers (light rams) is analyzed and illustrated by means of an example from the literature. An alternative method of computing the dynamic resistance of the ground by means of the measured set and the data of the hammer is presented, and evidence is given that it can be expected to apply equally well to light rams as to heavy ones. It is based on the graphodynamical method of treating longitudinal impact according to the complete pulse solution of the one-dimensional wave equation which was presented and developed in the previous articles of this series. One important parameter of this computing method is the elastic property of the ground. Suggestions are given for the experimental determination of this parameter. Contrary to common opinion this theory leads to the conclusion that high efficiency may well be obtained with light rams (compressed air hammers). In order to give best results, ram, capblock, helmet etc. should be constructed according to the demands of the pulse theory, and if this is done, a reduction of pile stresses can sometimes be obtained. Examples show that the assumptions of current dynamic formulae are better valid for heavy rams (short piles) than for light rams (long piles). Suggestions are given for further theoretical and experimental development of the new method.     

Lokale Subnormalteiler und ihr nilpotentes Residuum

Ohne Zusammenfassung     

Raman spectroscopy—A versatile tool for characterization of thin films and heterostructures of GaAs and AlxGa1−xAs

It is shown that Raman spectroscopy can provide useful information on characteristic properties of thin crystalline films of compound semiconductors. Crystal orientation, carrier concentration, scattering times of charge carriers, composition of mixed crystals and depth profiles can be studied in thin layers and heterostructures of GaAs and Al_xGa_1−xAs. The advantages and disadvantages of Raman scattering compared to conventional characterization methods are discussed.     

Über Graphen mit isomorphen Gerüsten

Ohne Zusammenfassung